Spring的web框架-外文翻譯

英文原文pringoffunctionalityandfeatures,whicharewell-organizedinmodulesinbelow.sectiondiscusseseachofmodulesinturn.heCoreisthemostfundamentalofframeworkandprovidestheDependencyInjectionallowingyoumanagefunctionality.basicherethewhichprovidesfactorypatternremovingtheneedforsingletonstodecoupletheandspecificationofdependenciesfromactualprogramlogic.OnofCoresitsContextbeansamanner,somewhatpackageinheritsitsfromaddssupportfortextmessagingresourceevent-propagation,resource-loadingandcreationofcontextsby,forexample,acontainer.TheDAOprovidesathedotediousJDBCcodingandofdatabase-vendorcodes.Also,JDBCpackageprovidesawaytodoprogrammaticaswellastransactiononlyinterfaces,butforallyourPOJOs(plainjavaTheORMpackageforpopularAPIs,includingJDO,HibernateiBatis.UsingtheORMyoucanuseallincombinationwithalltheoffers,declarativemanagementmentionedbefore.Spring'sprovidesAOPAlliancecompliantaspect-orientedprogrammingimplementationallowingdefine,forexample,andpointcutstofunctionalityshouldlogicallybesource-levelmetadatafunctionalityallkindsinformationyourcode,littlelikeattributes.Spring'sWebprovidesbasicintegrationsuchasmultipartfunctionality,initializationofservletausingtogetherwiththisisthepackageintegrateSpring'sprovidesaModel-View-Controllerimplementationforweb-applications.Spring'sMVCimplementationisjustimplementation,itprovidesaseparationdomainmodelcodeandallowsuseotheroflikevalidation.Spring'sframeworkdesignedathatdispatchesrequestswithconfigurablehandlerviewresolution,localethemeaswellforfiles.TheasimplejustModelAndViewhandleRequest(request,response)method.Thiscanbeforapplicationcontrollers,willthehierarchy,of,forAbstractController,ApplicationcontrollerswilltypicallybeofNoteyouanappropriateclass:Ifdon'taform,don'tneedFormController.Thisismajordifferencetocanuseobjectascommandorform-implementorderivefrombaseclass.datahighlyforexample,ittypemismatchesasvalidationerrorsbesystemerrors.needtobusinessobjects'propertiesasinformobjects,tohandleinvalidorconverttheInstead,itisoftentodirectlytoyourbusinessobjects.ThisisdifferenceStrutswhichisbuiltaroundrequiredbaselikeActionActionForm-foreverytypeofaction.ComparedWebWork,SpringobjectItnotionofacommandobject,getstoview.Themodelwillnormallyincludecommandbutarbitrarydata.Instead,aWebWorkallrolesintoonesingleWebWorkdoesallowyoutoexistingobjectsyourform,onlymakingthempropertiesActionclass.sameinstancethattheforevaluationpopulationintheThus,needstopropertiesActiontoo.arearguablytoomanyrolesforobject.Spring'sviewisextremelyflexible.AimplementationdirectlythereturningnullModelAndView.Inthenormalcase,ModelAndViewinstanceofMap,containingbeannamesand(likeacommandorform,isconfigurable,viabeanviaapropertiesorviayourownViewResolverimplementation.Theabstractforabstractionoftheviewtechnology,withoutanyAnycanbedirectly,whetherVThetransformedintoanappropriatesuchJSPrequestortemplatemodel..PluggabilityofotherimplementationsTherewhysomeprojectswillprefertoMVCimplementations.toleveragetheirexistinginskillsandtools.Intherelargebodyknowledgeavalailableforframework.ifyoulivewithStruts'itcanviablechoicefortheweblayer.ThesameappliestoWebWorkandotherwebMVCframeworks.Ifdon'twanttouseSpring'swebMVC,butsolutionsoffers,canwebframeworkofchoicewithSpringeasily.startaapplicationcontextitsaccessitviaitsattribute(orrespectivehelperwithinaorthataren't"plugins"dedicatedthepointofview,you'llsimplyuselibrary,withapplicationcontextinstanceentryAllregisteredallofcanatfingertipswithoutSpring'sMVC.withWebWorkthisitaddressesthemanythatthepureframeworksdon't,configurationdataaccessandtransactionSoableenrichyourapplicationwithamiddletierand/ordataaccessevenifyoujustwantuse,forthetransactionabstractionwithJDBCorHibernate.FeaturesSpringMVCSpring'swebwealthuniquewebsupportincluding:separationof-controller,validator,commandobject,formobject,handlermapping,viewrolecanbebyaspecializedPowerfulandconfigurationofframeworkandapplicationasJavaBeans,includingacrosscontexts,controllersbusinessobjectsandAdaptability,Usewhatevercontrolleryouneed(plain,form,wizard,multi-action,acustomone)forgiveninsteadofderivingacontrollerforeverything.Reusablebusinessnoneedforduplication.Youcanexistingobjectscommandorinsteadofmirroringintoextendparticularframeworkbasebindingvalidation-typemismatchesasapplication-levelthelocalizeddatebinding,String-onlyobjectswithparsingconversiontoobjects.handlermappingand-handlermappingandviewresolutionsimpleURL-basedstrategies.thanframeworksmandateatechnique.-name/valueMapintegrationwithtechnology.themeresolution,forJSPswithorSpringtaglibrary,forJSTL,supportforVelocitywithouttheforextraetc.Asimplebutpowerfultaglibraryavoidsanycost,allowingformaximumflexibilityinofDataAccessusingMappersintegrationwithOracleTopLink,OJBandSQLMaps:intermsofmanagement,DAOimplementationsupport,andstrategies.exampleforHibernate,isfirst-classwithofIoCconveniencefeatures,addressingHibernateintegrationAllofsupportforcomplywithSpring'stransactionandDAOThereareusuallytwointegrationSpring'sDAO'templates'orcodingDAOsHibernate/JDO/TopLink/etcInbothcases,DAOsbethroughInjectionandinresourceandmanagement.Spring'saddssupportwhenusingO/Rmappinglayerofyourchoicedataapplications.Firstall,knowthatusingsupportforyoudon'tgoallNowhatinvitedreviewSpringapproach,beforetheandofbuildingainfrastructureoftheO/Rsupport,nomatterwhatyou'reinlibraryaseverythingdesignedassetofreusableJavaBeans.insideanApplicationContextdoesprovideadditionalbenefitsinofofdeployment;asmostexamplesinsectionshowconfigurationinsideantheofSpringO/RDAOsEaseofSpring'sofittoswaptheimplementationsconfiglocationsofHibernateSessionFactoryDataSources,transactionmanagers,and(ifiteachofpersistence-relatedcodeinisolation.CommondatawrapexceptionsfromO/Rtoolchoice,themfromproprietarychecked)exceptionsacommonDataAccessExceptionhierarchy.allowshandlemostpersistenceexceptions,inappropriatelayers,withoutannoyingboilerplateandexceptionYouandhandleanywhereyouJDBCDBdialects)arealsotothehierarchy,youperformoperationswithJDBCwithinaconsistentprogrammingmodel.SpringapplicationcanthelocationandofSessionFactoryinstances,DataSources,SQLobjects,andrelatedresources.Thisvaluestomanageandchange.efficient,handlingofpersistenceresources.Forexample:codeusinggenerallyneedstosameHibernateforhandling.makesitbindSessioncurrentthread,eitheranatthecodelevelorbyexposingacurrentSession(forDAOsplainHibernate3API).Thussolvesoftherepeatedlyfromtypicalusage,orJTA).transactionSpringwrapO/Rwitheitherdeclarative,styleinterceptor,orexplicit'template'wrapperatIneithercase,semanticsforyou,andpropertransactionhandling(rollback,etc)inexceptionsistakenof.youalsothebenefittouseandswapvarioustransactionwithoutHibernate/JDOcodebeingaffected:forexample,betweenlocalJTA,withthesamefull(suchasdeclarativetransactions)inanbenefit,JDBC-relatedcodefullyintegratewithyoumapping.Thisisusefulfordataaccessnotformapping,suchasorofBLOBs,tosharecommontransactionswithO/Rmappingoperations.vendorlock-in,andallowimplementationstrategies.Whileisfree,itstillusesproprietaryAPI.couldarguethatisbitlightweight,it'sexcellentforinthatrequirecomplexO/Rstrategies.choice,desirabletoimplementfunctionalityusingstandardAPIs,inyouneedtoswitchanotherforfunctionality,ForofwithitsIoCwhichallowsyouswapinmapper/DAOobjectsdataaccessfunctionality,makesiteasytoallcodeinyourwithoutsacrificinganyofpowerofHibernate.Higherlevelcodedealingwiththeneedtoanythingaboutimplementation.approachhastheadditionalbenefitittointentionallyimplementwitha(i.e.someperformedusingHibernate,usingJDBC,othersusinginafashion,providinggreatbenefitsintermsofcontinuinguseorleveragingofeachtechnology.Theabstractionaformanagement.ThisabstractionisofthemostimportantofSpring'sabstractions,thefollowingtransactionAPIsasiBATISDatabaseLayerandJDO.asimpler,easierAPIformostofAPIswiththeSpringdataSpringtransactiondevelopershavehadfortransactionmanagement:orlocaltransactions.GlobalaremanagedbytheusingJTA.Localtransactionsforatransactionwithaconnection.Thishadprofoundimplications.Globaltransactionsprovidetheabilityworkwithresources.(It'smostuseasingletransactionresource)Withtransactions,applicationinvolvedintransactionmanagement,andacrossGlobaltransactionsasignificantdownside.CodeneedstouseJTA:cumbersomeAPIuse(partlyexceptionmodel).Furthermore,aJTAUserTransactionnormallyneedsbefromJNDI:thatweuseJTAtoJTA.ObviouslyalloftransactionslimitsreusabilityofapplicationasJTAnormallyinanserverTheuseglobalwasviaCMT(ContainerTransaction):aformoftransactionmanagement).EJBCMTremovesneedforJNDIlookups--althoughoftheuseofitselfnecessitatestheuseofJNDI.Itremovesmost--notall--needtowritetocontroltransactions.ThesignificantCMTis(obviously)tiedJTAapplicationenvironment;thatit'sonlyavailableifbusinesslogicinoratleastatransactionalEJBfacade.ThearoundEJBgeneralsothisanproposition,arealternativesforLocaleasiertoalsosignificantdisadvantages:cannotworkmultipleresources,andtendtotheprogrammingmodel.Forexample,thattransactionscannotrunwithinJTAresolvestheseItapplicationtouseprogramminganyenvironment.Youwriteyouronce,itcandifferenttransactionmanagementinenvironments.Springprovidesdeclarativetransactionmanagement.transactionmanagementpreferredbymostandrecommendedmostcases.Withmanagementworkwiththetransactioncanrunoveranyunderlyinginfrastructure.Withthepreferreddeclarativetypicallywritelittleorrelatedmanagement,dependonSpring'sorAPI.中文譯文包框架的最基礎(chǔ)部分，并供依賴注入DependencyInjection）特性來(lái)使你可管理Bean容器功能。這的礎(chǔ)概念是BeanFactory它提供Factory模式來(lái)消除對(duì)程序性單例的需要，并許你從序邏輯中分離出依賴關(guān)系的配置和描述。構(gòu)建于包Context包提供了一種框架式的Bean訪問(wèn)方式，有象注冊(cè)。包特性得自Beans包，添加了文本消息的發(fā)送，通過(guò)比如資源串，事件傳播，資源裝載的方式和Context的明創(chuàng)建，如通過(guò)Servlet容。DAO包提供了JDBC的抽象層它消除冗長(zhǎng)的JDBC碼和解析數(shù)據(jù)庫(kù)廠商特有的錯(cuò)誤代碼。該包提供了一種方法現(xiàn)編程性和聲明性事務(wù)管理，不僅僅是針對(duì)實(shí)現(xiàn)特定接口的類，而且所有的POJO。ORM包為流行的關(guān)系－對(duì)象映射APIs提供了集成層，包括JDOHibernate和iBatis。通過(guò)ORM包你可與所有Spring供的其他特性相結(jié)合來(lái)使用這些對(duì)/關(guān)系映射，如前邊提到的簡(jiǎn)單聲明性事務(wù)管理。Spring的AOP包供與AOP聯(lián)兼容的面向方面編程實(shí)現(xiàn)，允許你定義，如法攔截器和切點(diǎn)，來(lái)干凈地給從邏輯上說(shuō)應(yīng)該被分離的功能實(shí)現(xiàn)代碼解耦。使用源碼級(jí)的元數(shù)據(jù)功能，你可將各種行為信息合并到你的代碼中，有點(diǎn)的attribute。Spring的Web包供了基本的面向Web綜合特性Multipart功，使用Servlet監(jiān)聽(tīng)器的Context的始化和面向Web的ApplicatinContext。當(dāng)與WebWork或Struts一起使用Spring時(shí)這個(gè)包使Spring可其他框架結(jié)合。Spring的包供了面Web應(yīng)的Model-View-Controller實(shí)。Spring的MVC實(shí)不僅僅是一種實(shí)現(xiàn)，提供了一種model代碼和webform的清晰分離，這使你可使用Spring框的所有其他特性，如校.Spring的web框架是圍繞分發(fā)）設(shè)計(jì)的，DispatcherServlet將請(qǐng)求分發(fā)到不同的處理器，框架還包括可配置的處理器映射，視圖解析化主題解析，還支持文件上傳。缺省的處理器是一個(gè)簡(jiǎn)單的控制器Controller）口，這個(gè)接口僅僅定義了ModelAndViewhandleRequest(request,response)法你以實(shí)現(xiàn)這個(gè)接口生成應(yīng)用的控制器，但是使用Spring提供的一系列控器實(shí)現(xiàn)會(huì)更好一些，比如AbstractControllerAbstractCommandController，和SimpleFormController。應(yīng)用控制器一般都從它們繼承。注意你需要選擇正確的基類：如果你沒(méi)有表單，你就不需要一個(gè)FormController。是和Structs的個(gè)主要區(qū)別。你可以使用任何對(duì)象作為命令對(duì)象或表單對(duì)象：不必實(shí)現(xiàn)某個(gè)接口或從某個(gè)基類繼承。Spring的數(shù)綁定相當(dāng)靈活，如，它認(rèn)為類型不匹配這樣的錯(cuò)誤應(yīng)該是應(yīng)用級(jí)的驗(yàn)證錯(cuò)誤，而不是系統(tǒng)錯(cuò)誤。所以你不需要為了處理無(wú)效的表單提交，或者正確地轉(zhuǎn)換字符串，在你的表單對(duì)象中用字符串類型重復(fù)定義你的業(yè)務(wù)對(duì)象屬性該直接綁定表單到業(yè)務(wù)對(duì)象上。這是和Struts的另個(gè)重要不同Struts是圍繞象和ActionForm這樣的基類構(gòu)建的，每一種行為都是它們的子類。和WebWork相比，Spring將對(duì)象細(xì)分成不同的角色：它支持的概念有控制器（Controller選命令對(duì)（Object）或表單對(duì)象（Object及傳遞到視圖的模型Model型僅包含命令對(duì)象或表單對(duì)象，而且也包含任何引用數(shù)據(jù)。但是WebWork的將有這些角色都合并在一個(gè)單獨(dú)的對(duì)象里允你在表單中使用現(xiàn)有的業(yè)務(wù)對(duì)象是只能把它們定義成不同Action類的bean屬性重的是，在運(yùn)算和表單賦值時(shí)，使用的是同一個(gè)處理請(qǐng)求的Action實(shí)例。因此，引用數(shù)據(jù)也需要被定義成Action的bean屬性這樣在一個(gè)對(duì)象就承擔(dān)了太多的角色。對(duì)于視圖：Spring的圖解析相當(dāng)靈活。一個(gè)控制器實(shí)現(xiàn)甚至可以直接輸出一個(gè)視圖作為響應(yīng)，這需要使用null返ModelAndView在一般的情況下，一個(gè)ModelAndView實(shí)例包含視圖名字和模型映射表，模型映射表提供了bean名字及其對(duì)象（比如命令對(duì)象或表單對(duì)象，引用數(shù)據(jù)等等）的對(duì)應(yīng)關(guān)系。視圖名解析的配置是非常靈活的，可以通過(guò)bean的名字，屬性文件或者你自己的ViewResolver來(lái)實(shí)現(xiàn)。抽象的模型映射表完全抽象了表現(xiàn)層，沒(méi)有任何限制Velocity，者其它的技術(shù)——任何表現(xiàn)層都可以直接和Spring集成。模型映射表僅僅將數(shù)據(jù)轉(zhuǎn)換成合適的格式，比如JSP求屬性或者模模型。MVC實(shí)現(xiàn)的可擴(kuò)展性許多團(tuán)隊(duì)努力爭(zhēng)取在技術(shù)和工具方面能使他們的投入更有價(jià)值是現(xiàn)有的項(xiàng)目還是新的項(xiàng)目都是這樣。具體地說(shuō)Struts不有大量的書(shū)籍和工具，而且有許多開(kāi)發(fā)者熟悉它。因此如果你能忍受Struts的架構(gòu)性缺陷，它仍然是web層一很好的選擇WebWork和其它web框架也是這樣。如果你不想使用Spring的webMVC框架，而僅僅想使用提供的其它功能，你可以很容易地將你選擇的web框架和Spring結(jié)合起來(lái)。只要通過(guò)Spring的ContextLoadListener啟動(dòng)一個(gè)Spring的根用上下文且通過(guò)它的ServletContext屬性（或者Spring的種幫助方法）在Struts或WebWork的Action中訪。注意到現(xiàn)在沒(méi)有提到任何具體的“plugins”因此這里也沒(méi)有提及如何集成：從層角度看，你可以僅僅把Spring作一個(gè)庫(kù)使用，根應(yīng)用上下文實(shí)例作為入口。所有你注冊(cè)的bean和的務(wù)可以在沒(méi)有Spring的webMVC下被訪問(wèn)Spring并沒(méi)有在使用方法上和或WebWork爭(zhēng)，它只是提供單一web框架沒(méi)有的功能，從bean的配置到數(shù)據(jù)訪問(wèn)和事處理以你可以使用Spring的中層（或者數(shù)據(jù)訪問(wèn)層來(lái)增強(qiáng)你的應(yīng)用，即使你只是使用象JDBC或Hibernate務(wù)抽象這樣的功能。SpringMVC框架的特點(diǎn)如果僅僅關(guān)注于web方面的支持Spring有下面一些特點(diǎn)：清晰的角色劃分：控制器，驗(yàn)證器，命令對(duì)象，表單對(duì)象和模型對(duì)象；分發(fā)器，處理器映射和視圖解析器；等等。直接將框架類和應(yīng)用類都作為配置，包括通過(guò)應(yīng)用上下文配置中間層引用，例如，從web控制器到業(yè)務(wù)對(duì)象驗(yàn)證器的引用?？蛇m應(yīng)性但具有強(qiáng)制性：根不同的情況，使用任何你需要的控制器子類（普通控制器，命令，表單，向?qū)?，多個(gè)行為，或者自定義的），而不是要求任何東西都要從Action/ActionForm繼承可重用的業(yè)務(wù)代碼不需要代碼重復(fù)可使用現(xiàn)有的業(yè)務(wù)對(duì)象作為命令對(duì)象或表單對(duì)象，而不需要在的子類中重復(fù)它們的定義。可定制的綁定和驗(yàn)證將類型不配作為應(yīng)用級(jí)的驗(yàn)證錯(cuò)誤可以保存錯(cuò)誤的值以及本地化的日期和數(shù)字綁定等不只能使用字符串表單對(duì)象動(dòng)解析它并轉(zhuǎn)換到業(yè)務(wù)對(duì)象?？啥ㄖ频奶幚砥饔成?，可定制的視圖解析：靈活的模型可以根據(jù)名/值映射，處理器映射和視圖解析使應(yīng)用策略從簡(jiǎn)單過(guò)渡到復(fù)雜，而不是只有一種單一的方法?？啥ㄖ频谋镜鼗椭黝}解析，支持JSP無(wú)論有沒(méi)有使用Spring標(biāo)簽庫(kù)，支持JSTL，支持不需要額外過(guò)渡的Velocity，等等。簡(jiǎn)單而強(qiáng)大的標(biāo)簽庫(kù)，它盡可能地避免在HTML生時(shí)的開(kāi)銷，提供在標(biāo)記方面的最大靈活性。使用ORM工進(jìn)行數(shù)據(jù)訪問(wèn)Spring在資管理，DAO實(shí)支持以及實(shí)物策略等方面提供了與Hibernate,JDO和iBATISSQL映的集成。對(duì)Hibernate，Spring使了很多IoC的便的特性提供了一流的支持，幫助你處理很多典型的Hibernate整合的問(wèn)題。所有的這些都遵守Spring通用的事務(wù)和DAO異常體系。當(dāng)您選擇使用O/R映來(lái)創(chuàng)建據(jù)訪問(wèn)應(yīng)用程序的時(shí)候Spring的加部分就會(huì)向您提供重要的支持。首先你應(yīng)該了解的是，一旦你使用了Spring對(duì)O/R映射支持，你不需要親自作所有的事情在決定花力氣冒著風(fēng)險(xiǎn)建造類似的內(nèi)部底層結(jié)構(gòu)之前們都建議您考慮和利用Spring的決案。不管你使用的是何種技術(shù)，大部分的O/R映支持都可以以樣式被使用，因?yàn)樗械臇|西都是被設(shè)計(jì)成一組可重復(fù)利用的JavaBeans。在ApplicationContext和BeanFactory中使用更是提供了配置和部署簡(jiǎn)單的好處，因此，這一章里的大多數(shù)例子都是在ApplicationContext中置。使用構(gòu)你的ORM應(yīng)用好處包:測(cè)試簡(jiǎn)單.Spring的IoC使很易替換掉不同的實(shí)現(xiàn)HibernateSessionFacotory的位置datasource,事務(wù)管理映射對(duì)象的實(shí)現(xiàn)樣就很容易隔離測(cè)試持久化相關(guān)代碼的各個(gè)部分。異常包裝。Spring能包裝Hibernate異，把它們從專有的checkedexception變?yōu)橐唤M抽象的runtimeexception這樣你就可以僅僅在恰當(dāng)?shù)膶犹幚泶蟛糠值牟豢苫謴?fù)的異常你免了很多討厭的catch/throw以異常聲明還是可以在你需要的地方捕捉和處理異?；匾幌翵DBC常（包括與DB相的方言）被轉(zhuǎn)變?yōu)橥瑯拥漠惓ｓw系就意味著你可以在一致的編程模型中處理JDBC操作。通用的資源管理。Spring的applicationcontext能處理諸如Hibernate的SessionFactory，JDBC的datasource，iBatis的SQLMaps配置象以及其他相關(guān)資源的定位和配置。這使得這些配置的值很容易被管理和修改Spring提了有效，簡(jiǎn)單和安全的HibernateSession處。般的使用Hibernate的代碼則需要使用同一個(gè)HibernateSession對(duì)以確保有效和恰當(dāng)?shù)厥聞?wù)處理。而Spring讓我們可以很容易透明地創(chuàng)建和綁定一個(gè)session到前線程你以使用以下兩種辦法之一聲明式的